Matter - anything that has mass and takes up space. Physical change - any change that alters the form or appearance of a substance but doesn’t make it into another substance. Chemical change - a change in matter that produces one or more new substances. Occurs when old bonds break and new bonds form.
Evidence for Chemical Reactions a. Precipitate- a solid that forms. b. Color change c. Gas production d. Change in energy- :Endothermic reaction-absorbs energy, temperature goes down. :Exothermic reaction-releases energy, temperature goes up.
Reactants -The substances that undergo change in a Chemical Reaction. Products -The new substances formed by a reaction. Chemical equation - the short, easy way to show a chemical reaction using symbols. 2 H 2 + O 2 2 H 2 O Coefficient - the number placed in front of a chemical formula in an equation.
Conservation of Matter- during a chemical reaction, matter is neither created nor destroyed. The number of atoms on the left side of the equation must equal the atoms on the right side. CaCO 3 CaO + CO 2
Acid -tastes sour, reacts with metals, turns litmus paper red. Corrosive -wear away at materials. :acid rain Hydrogen ion (H + )- an atom of hydrogen that has lost its electron. An acid produces hydrogen ions in water.
Base - taste bitter, feels slippery, turns litmus paper blue. Hydroxide ion (OH - ) - a negative ion, made of oxygen and hydrogen. A base produces hydroxide ions in water. Indicator - a compound that changes color when in contact with an acid or base. (Litmus paper, cabbage juice)
pH scale - a range of values from 0-14. It shows the concentration of hydrogen ions in a solution. A low pH=high concentration of hydrogen ions. A high pH=low concentration of hydrogen ions. Neutral - It is neither an acid or a base. The pH is 7. Pure water is neutral.
Neutralization - a reaction between an acid and a base. The pH would be close to 7. Salt - any ionic compound that is made from the neutralization of an acid with a base.