Beamer : la taille des blocs est-elle modulable ?

\documentclass[english,10pt]{beamer}
\usetheme{JuanLesPins}
\setbeamercovered{transparent}
% \definecolor{vertmoyen}{rgb}{0.20,0.43,0.09}
\definecolor{bleuklein}{rgb}{0.30,0.10,0.95}
\usecolortheme[named=bleuklein]{structure}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[french]{babel}
\setbeamersize{text margin left = 2mm, % normalement c'est 1 cm
    text margin right = 2mm % normalement c'est 1 cm
}
% \usepackage[left=10mm,right=10mm,top=20mm,bottom=20mm]{geometry}
\usepackage{color}
\usepackage{xcolor}
% \usepackage[dvipsnames,svgnames]{xcolor}
\usepackage{pgf}
\usepackage{tikz}
\usepackage{graphicx}
% \usepackage{picins}
\DeclareGraphicsExtensions{.jpg,.pdf,.png}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{url}
\usepackage{setspace}
\usepackage{gensymb}
\usepackage{mathrsfs}
\usepackage{chemfig}
\usepackage{pgfplots}
\usepackage{siunitx}
\usepackage{booktabs}
\usepackage{tabularx}
\usepackage{array}
\usepackage{ragged2e, makecell, mhchem}
\usepackage{fancyhdr}
\pagestyle{fancy}
\pagestyle{empty}
% \usepackage{caption}
% \usepackage{columns}

\begin{document}

\begin{frame}[shrink=60]
\frametitle{Amination reaction}
\framesubtitle{Quantitative analysis of amine fonctions II : conductimetry}
\begin{block}{chemical equation}
    \begin{center}
\begin{tikzpicture}
\draw[->,thick,>=stealth] (4,0.5) -- (8,0.5);
\draw (0.5,0.5) node {$NH_{3}^{+} - R - NH_{3}^{+}\, (aq) +\, 2\, HO^{-}\, (aq)$};
\draw (11,0.5) node {$NH_{2} - R - NH_{2}\, (aq) +\, 2\, H_{2}O$};
\end{tikzpicture}
    \end{center}
\end{block}
\begin{block}{Example of COS 16}
\begin{center}
\begin{tikzpicture}[scale=0.8]
    \begin{axis}[axis x line=bottom,axis y line = left, grid=major,
    xlabel=\scalebox{1.2}{soude volume ($mL$)},
    ylabel=\scalebox{1.2}{$\sigma\, (\mu S.cm^{-1}$)},
    xmin=0,
    xmax=16,
    ymin=2,
    ymax=9.5,
    mark size=0.2pt,
    width=1.0\textwidth]
    \addplot table [x=volume,y=sigma,col sep=tab] {dosage_conductimetrie_COS16_2019_02_01.txt};
    \end{axis}
\end{tikzpicture}
% \caption{COS16 dosage}
\end{center}
\end{block}
\end{frame}
\end{document}