What is Chemistry?

List the four evidences of chemical change.

1. The Evolution of a Gas 2. The Formation of a Precipitate 3. The release or absorption of Energy 4. A color change in the reaction system

Chemical

A chemical is any substance that has definite composition. Changes in chemicals, or chemical reactions, take place all around us.

Chemical Reactions

A chemical reaction rearranges the atoms that make up the reactant or reactants. After a chemical reaction, the same atoms are present in the product or products. Atoms are not destroyed or created. So, mass does not change during a chemical reaction.

A color change in the reaction system

A color change in a reaction system, such as when an indicator changes color, may indicate that a chemical reaction has occurred and new substances have formed.

Reactants

A substance or molecule that participates in a chemical reaction.

Products

A substance that forms in a chemical reaction.

Chemical

Any substance that has a definite composition-It's always made of the same stuff no matter where chemicals come from.

Explain how chemicals and chemical reactions are an important part of your life.

Because it is necessary for living things to grow. It is important for us to digest food inside us. Striking a match requires chemical reactions.

Explain the choice in question #7.

Because the Mercury (II) oxide changed into Mercury and Oxygen with the chemical change.

Explain the choice you made in #3.

Because the sugar molecules were mixed with tea but they did not change into another form. The particles are still the same (sugar.)

Between what Celsius temperatures is water a liquid?

Between 0 degrees Celsius and 100 degrees Celsius. Water exists as a liquid

Chemical Reaction

Changes in chemicals that are taking place inside you and around you.

Burning Wood

Chemical Change

Cooking an egg

Chemical Change

Gasoline Burning

Chemical Change

Lighting a match

Chemical Change

Milk souring

Chemical Change

bleaching a stain

Chemical Change

Observations of a Chemical change

Chemical changes sometimes produce a gas, which you can detect by observing bubbles or by a change in odor.

Is dissolving sugar in tea a physical or chemical change?

Dissolving sugar in tea is a physical change.

Gases

Gases have variable volume and variable shape. Gas particles may move a part to fill any container they occupy. This behavior occurs because gas particles are far apart and are not strongly attracted to one another.

Chemical Changes

In a Chemical change, the identities of substances change and new substances form.

An example of Chemical Change

In the word equation, hydrogen + oxygen + heat ----- water, hydrogen is a reactant, and water is a product.

Liquids

Liquids have a fixed volume but a variable shape. This situation occurs because particles in a liquid are held loosely and can slip past each other.

Liquid

Liquids have fixed volume but not a fixed shape. The particles in a liquid are not held together as strongly as those in a solid

Is the mercury (II) oxide a product or reactant in that reaction?

Mercury (II) oxide is a reactant.

Is the mercury (II) oxide undergoing a chemical or physical change?

Mercury (II) oxide is undergoing into a chemical change.

Chopping wood

Physical Change

Ice melting

Physical Change

Water evaporating

Physical Change

breath fogging a mirror

Physical Change

Physical Changes

Physical Changes are changes in which the identity of a substance does not change. Thus the changes of state are physical changes.

Physical Change

The changes in which the identity of a substance doesn't change.

Solids

The characteristics of a solid include fixed volume and shape. Particles that make up solids are held tightly in a rigid structure, so the particles can vibrate only slightly flow past each other.

Chemical Change

The identities of substances change and new substances form.

What is the name and chemical formula of the top chemical made in the United States by weight? What is it used for?

The name of one of the top eight chemicals is Sulfuric Acid. Its chemical formula is H2SO4. It is used for the production of fertilizer, metal processing, petroleum refining.

What is the name and color of the precipitate made when solutions of sodium sulfide and cadmium nitrate are mixed?

The name of the new gas is cadmium sulfide. The color is yellow.

States of Matter

The physical forms of matter which are solids, liquids, gasses and plasma.

Particles

The type and arrangement of particles in a sample of matter determine the properties of matter. Most of the matter you encounter is in one of three states of matter.

When mercury (II) oxide is heated it decomposes into what two chemicals?

They decompose into two chemicals-Mercury and Oxygen

Solid

They have a fixed volume and shape

Gas

They have neither fixed volume nor fixed shape. Gas particles weakly attract to one another and move independently at high speed.

Energy released during a Chemical reaction

When energy in released during a chemical reaction, temperature of the surroundings increases. Chemical reactions may also absorb energy, which is indicated by a decrease in temperature.

Mixtures

When two clear solutions mix and a precipitate forms, the mixture becomes cloudy.

Percipitate

a solid that forms from solution during a chemical reaction