3.1: important examples of chemical change

explosion (sudden release of gases from solids), dry cell battery (release energy slowly and store it), photosynthesis (biochemical), cellular respiration (biochemical)

what are some examples of chemical change?

new substances produced in a chemical reaction. Have completely different properties from its reactants.

what are products?

It states that the total mass of the reactants in a chemical reaction equals the total mass of the products. (total number of atoms present before a reaction equals the total number of atoms present after a reaction)

What is the law of conservation of mass?

Antoine Lavoisier in 1789

Who created the law of conservation of mass?

Biochemical reactions are essential to life, can be exothermic or endothermic, happens at an organisms' internal temperature, and they are almost always helped by enzymes (biological catalysts)

what are biochemical reactions and what do they do?

- Photosynthesis: a complex process that captures the sun's light and allows a plant to use this energy to make sugar molecules (endothermic reaction). - Cellular respiration: the reverse of photosynthesis. Animals and plants use this to release energy that is then used to drive all the chemical reactions in their tissues and organs (exothermic reaction).

what are some examples of biochemical reactions?

- cold pack: contains chemicals that absorb energy directly from the environment. When you squeeze the package, you break a container inside the pack that keeps the chemicals separated from one another. When the container breaks, the chemicals mix and react. As they react, they absorb energy and the whole mixture cools down.

what are some examples of endothermic reactions?

it can be very sudden and dramatic (like an explosion) or very slow and steady (like in a rising cake). Ex: automobile air bags - sodium azide (solid compound) is heated and ignited by an electrical signal when a front-end collision occurs. The air bag inflates, and nitrogen gas is produced because a solid suddenly decomposed.

what are some reactions that form gases? And what are its characteristics?

glue: it contains resin and a hardener. If you mix the two chemicals together, it will harden after about five minutes. Each of the molecules in the resin has several places where sit can join with the molecules in the hardener. A web of links forms, causing the whole mixture to form one large molecule. because the bonds are really strong, it will hold its shape and bind to many materials that are otherwise difficult to glue together.

what are some reactions that form solids?

- all ionic compounds are solid at room temperature. - An ionic compounds that is very soluble is shown as aqueous (when dissolved in water) - An ionic compounds that is slightly soluble is shown as a solid, even when it's in water. - molecular compounds are hard to predict. The smaller the molecules are, the more they tend to be gases. The larger they are, the more they tend to be liquids and then solids.

what states are compounds in?

it occurs when a substance/substances react in a chemical reaction to create a new substance.

what is chemical change?

chemical reaction that absorbs energy

what is endothermic reaction?

solid (s), liquid (l), gas(g), and aqueous (aq)

what are the four states that often appears in chemical formulas?

- metals are all solids, except for mercury. - most diatomic elements are gases except for bromine, and iodine.

what states are the elements in?

substances that reacts in a chemical reaction to form another substances(s)

what are reactants?

- it produces new substances that has its own properties (state, density, colour, melting point) - it involve the flow of energy (can be detected by change in temperature) - When new substances form, sometimes change of state can be observed (formation of gas (bubbles) or a solid (precipitate)). - all are consistent with the law of conservation of mass.

what are the characteristics of all chemical reactions?

it refers to the substance's state at room temperature (25 degrees), unless other information is presented.

what does the state subscript refer to?

chemicals that speed up a reaction but are not used up by it.

what is a catalysts?

a chemical reaction that releases energy, usually in the form of heat, light, or electricity.

what is exothermic reactions?

- lead-acid storage battery: It discharges during ignition and charges while the vehicle is running. While it's discharging, an exothermic reaction occurs. The battery contains sulfuric acid, which works as an electrolyte to carry an electric current between the solid chemicals inside the battery. When the vehicle is started, the battery releases energy in the form of electricity (discharging). - Combustion: a chemical chemical reaction that occurs when oxygen reacts quickly with a substance to form a new substance(s) and give off energy (AKA burning).

what are some examples of exothermic reactions?